The present invention relates to a carousel-type apparatus for manufacturing threaded plastics caps by compression molding.
Such apparatuses are already known, for example from publication PCT/EP95/03644 in the name of the Applicant, from German publication no. 2,007,777, from European publications no. 91,653 and 162,456, and from U.S. Pat. Nos. 2,155,316, 2,891,281, 4,343,754, 4,497,765, 4,640,673, 5,451,360, 5,554,327.
Compression molding apparatuses generally comprise a carousel which can rotate about a vertical axis and on which a plurality of molding assemblies are installed so as to be spaced one another by an equal angle. Each assembly comprises an upper male mold half (punch) which is aligned with a lower female mold half.
A dose of semifluid plastic material is introduced in the female mold half and compressed by means of a relative motion of the two mold halves in order to obtain the item.
In the manufacture of caps for closing containers, the molded cap, which remains attached to the punch after the opening of the mold halves, is removed by means of an ejector.
In the case of caps provided with an internal thread, removal occurs by utilizing the elasticity of the material, which allows to force the cap on its threads.
In order to prevent the caps from being damaged due to the forcing with which they are removed, solutions have been proposed which entail unscrewing the punch while the cap is rotationally locked or unscrewing the cap from the punch by means of an external element. Solutions for removing the caps from the molds are known from Japanese publications no. 62-264923 and 4-113820 and from U.S. Pat. Nos. 2,363,308, 2,799,049, 3,712,786, 3,856,255, 4,496,302, 5,383,780.
However, conventional solutions are applied exclusively to injection molding machines and are constructively too complicated and heavy to be used in carousel-type apparatuses, in which the opening of the mold and the expulsion of the caps must be actuated in very specific angular positions and in which it is important to reduce the rotating mass.
The aim of the present invention is therefore to devise a carousel-type apparatus in which said caps are rotated with respect to the male mold half in order to remove them.
Within the scope of this aim, an object of the present invention is to provide a carousel-type apparatus in which the molds are structurally simple, reliable in operation and easily adaptable to the characteristics of the caps to be manufactured.
This and other objects are achieved with an apparatus whose characteristics are defined in the appended claims.